Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$41.91	12.699%	$47.2322	$47.23	$47.25	$47.20
Purchase #2	$196.93	13.498%	$223.5116	$223.51	$223.50	$223.50
Purchase #3	$206.70	4.766%	$216.5513	$216.55	$216.55	$216.60
Purchase #4	$147.51	13.789%	$167.8502	$167.85	$167.85	$167.90
Purchase #5	$198.65	12.371%	$223.225	$223.23	$223.25	$223.20
Purchase #6	$191.89	7.397%	$206.0841	$206.08	$206.10	$206.10
Purchase #7	$188.46	8.282%	$204.0683	$204.07	$204.05	$204.10
7 purchase totals =	$1,172.05		$1,288.5227	$1,288.52	$1,288.55	$1,288.60